Breech block locking bolt for a gun



J. P. JARVIS ETAL BREECH BLOCK LOCKING BOLT FOR A GUN Dec. 22, 1964 2 Sheets-Sheet 1 Filed Dec. 26, 1963 W. Q\ N MN 7 mu; f Q X i M a 3 U. w Q 5 om 8 e\\ R F mw b I Z M m Q INVENTORS ,JAV P JARVIS EDWIN S. VARTAN/AN A TTORNEV 1366- 22, 1964 J. P. JARVIS ETAL BREECH BLOCK LOCKING BOLT FOR A GUN 2 Sheets-Sheet 2 Filed Dec. 26, 1963 IN V EN 1 CR5 JAY P JARVIS EDWIN S. VARTAN/AN A 7'TORNEV United States Patent 3,161,977 BREECH BLOCK LOCKENG BOLT FOR A GUN Jay P. Jarvis, North Bradford, and Edwin S. Vartanian, North Haven, Conn, assignors to 81in Mathieson Chemical Corporation, a corporation of Virginia Filed Dec. 25, 1963, Ser. No. 333,304 12 Claims. (CI. 42-21) This invention relates to an improvement in firearms and more specifically to repeating types of firearms having a magazine.

The improvement relates particularly to a gun of the lever action type shown in US. Patent No. 524,702 and well known for over half a century for its ruggedness, compactness, ease of handling, safety, and reliability.

In accordance with this invention the action of the gun is improved by a change in the locking bolt which serves to hold the breech block shut and make other actuating connections in the action of the gun.

A preferred embodiment described herein is shown in the accompanying drawing in which:

FIG. 1 is an elevational right side view of a portion of the gun shown partly in cross section in its open position;

FIG. 2 is a left side view corresponding to FIG. 1 but showing the gun in its closed position and fired;

FIG. 3 is a transverse view in cross section taken on line 3-3 of FIG. 2 showing the locking bolt and its connection to the operating link; and

FIG. 4 is an enlarged view of the lower end of the locking block and one of its trunnions showing how it mates with a portion of the link in the position shown in FIG. 2.

The gun has a hollow receiver 1. Mounted to the front end of the receiver are the barrel 2 of the gun and a magazine tube 3. A gun butt stock 4 is mounted at the rear end of the receiver. A finger lever 5 projects from the bottom.

7 Along the top of the receiver there is an opening at which a breech block 6 is slidably mounted for longitudinal movement such that in a forward position of the breech block the top of the receiver is closed, while in the rearward position the opening is uncovered to form an ejection port 7.

V Opening and closing of the ejection port, cocking of the gun, and feeding of the ammunition are done by a lever action imparted manually by means of the operating finger lever 5 which is attached at its upper end by means of a cross pin 8 to the breech block 6. Lever 5 also is a trigger guard.

At the bottom of the receiver there is provided an operating link 10 pivoted at its front end to the receiver on link pin 12. The lever is both slidably and pivotally connected to the link 10 by means of roll pin 13 extending intothe lever slot 14 formed intermediate the ends of the lever. The block 6 is reciprocated and the port 7 controlled by this linkage.

' In the magazine tube are the usual coil spring 15 and magazine follower 16 forfeeding the cartridges into the receiver.

The action of the gun and the firing mechanism are housed in the hollow of the receiver and a hollow formed in the portion of the stock mounted between an upper tang 17 integral with the receiver and a lower tang 19, which is a separate piece connected at its front end to the rear of the receiver at the hammer pivot pin 20. Ex tending from tang 19 is the trigger 23.

Hammer 25 is mounted pivotally on the hammer pivot pin 20. Rotation of the hammer about this pin back to the cocked position shown in FIG. 1 occurs against the bias of spring 26, upon engagement between the hammer and the rear end of the breech block as the latter is moved to the rear. Mounted on the lower tang for movement about the same center pin are the sear 28, engaging with the hammer 25 to hold it cocked, and also the trigger 23 for rocking the sear out of hammer engagement against the bias of a seat spring 29, which is also carried by tang 19 as is the hammer spring 26, to release the hammer.

Mounted pivotally on carrier pin 30 is a carrier 31 for lifting a magazine-fed cartridge into alignment with the barrel bore and retracted block 6.

The link 10 has a magazine cutoff 11 which rises when the rear end of the link is lowered as in FIG. 1 to prevent another cartridge being fed until the gun is closed. This also prevents interference between an incoming cartridge and carrier 31, the extreme forward end of which clears the cutoff 11 and rests upon the forward end of the link 10 not only when the gun is closed but also when the lever action is beginning to open to receive a cartridge up on the carrier 31. The other end of the carrier is slotted at 32 to clear the portion of the lever extending between cross pin 8 and roll pin 13 until the lever is pulled back and the gun closed whereupon this lever portion engages with the carrier in carrier slot 32 and pushes down the carrier end, until finally impelled by carrier spring 33 down on the forward end of the link 10 for reception of not more than one more cartridge.

Spring 33 as heretofore bears down on a carrier toggle lug 35 extending up from one side of the carrier at pin 30.

As the block 6 is slid back, engagement is made between a shoulder on the block and a detent 34 extending up from the other side of the carrier near pin 30. This together with the bias of spring 33 on lug 35 tilts the cartridge received on the carrier upwardly. The carrier as heretofore is thus pivotally raised and lowered about carrier pin 3% and finally impelled up or down by the action between carrier spring 33 and carrier toggle lug 35 for the final bias either upwardly in the position of FIG. 1 or downwardly in the position of FIG. 2.

Mounted at the rear of the receiver is the breech block locking bolt 40 carried in guide grooves 41 and 42 formed in the opposite walls of the receiver and extending at an angle inclined rearwardly. Under the action of the lever and operating link the locking bolt is adapted for movement up and down in these grooves to the positions shown in FIGS. 1 and 2.

Carried captive in the bolt with limited sliding motion is a striker 37 for receiving the blow of the hammer 25 and passing the blow on to the firing pin 39 mounted in block 6, provided bolt 40 is sufficiently elevated.

In its fully elevated position bolt 4-59 extends back of the breech block as a wedge for bolstering the block shut when the finger lever is in the closed position. For this purpose the upper end of bolt 40 has a front wedge surface 45 in the form of a slot for receiving and acting on a mating inclined surface 46 at the rear end of the breech block 6: The bolt is driven through a slidabie pivot connection to the link.

The lower end of the locking bolt takes the form of a narrow shank as shown in FIG. 3 at the end of which there are mounted outwardly extending trunnions 51 and 52 for connecting slidably with the rear end of the operating link 10, which has for this purpose a T-slot providing opposing slide grooves 53 and 54 receiving the trunnions 51 and 52, respectively. Heretofore, these trunnions have been formed by the projecting ends of a round pin. This, after a time of use, has caused accentuated wear at points in the slots 53 and 5 which cannot be readily corrected, although wear on the round pin may be compensated by replacement with a new pin as shown in aforementioned U.S. Patent No. 524,702.

Manufacture and replacement of the round trunnions is costly. In the available space of the slots 53 and 54, while round trunnions do permit a rocking action, they do not provide the largest, strongest, and most wearresistant connection.

Although wear of both trunnions and even breakage of one does not prevent functioning in the rugged mechanism of this type of firearm, wear does cause rattle due to increased lost motion and also some loss in smoothness of o eration of the lever action due to development of worn points in slots 53 and 4. By this invention this is avoided in a most economical way.

Since the greatest stress and bulk of the wear between the trunnions and the link occurs on impact at the upper terminal of the locking bolt travel (gun closed) where the friction is greatest and where static friction must be overcome to initiate bolt travel to the lower terminal gun opened), this invention contemplates trunnions offering a flat surface contact at least adjacent the upper terminal of this travel.

One way is to provide rectangular blocks as rotatable trunnions each mounted pivotally in bolt 4t} each on a round shank and each having a pair of opposed parallel sides riding in the parallel sided internal slots or grooves 53 and 54 of the T-connection of the link. This would be expensive.

Another and preferred way is to form fixed trunnions of diamond or lozenge shape, or truncated diamond or lozenge shape as shown in FIGS. 1, 2, and 4, each integral with the bolt. These shapes may be also identified as a rhomboidal hexagonal shape. A regular hexagon may be used in some cases.

Left trunnion 51 of the shape preferred is shown in greater detail in FIG. 4. The invariant is a pair of parallel sides 61 and 62 slidably fitting on Ways in parallel side slots 53 and 54 of the link at the T-slot connection. Rear bottom side of bears the thrust exerted by the bottom of slot 53 of the link lit at the closing of the gun where hi h dynamic friction between the bolt and block is encountered and being resisted. Front top side 62 bears the thrust exerted by the top of slot 53 at the start of opening of the gun where both high static and dynamic resistance must be overcome.

At the top of bolt travel, fiat side all not only tends to avoid overtravel which would unnecessarily increase wedge forces occurring between the bolt and block but also tends to wear hat to match whatever little remaining wear would occur normally between the bolt and block.

Paired with main bearing sides 61 and 62 are parallel relief sides 1 and '72 respectively each cut at the least an le needed to give the necessary relief or clearance to allow the trunnion to turn in its link groove 53 during travel of the bolt dd downwardly. Sides s1 and '71 thus form an obtuse dihedral angle as do 62 and 72 such that the supplement of that angle provides the needed relief angle.

The ridge 81 between fiat surfaces 61 and 71 at the bottom of the trunnion is rounded oif a bit preferably by as large as possible a radius of curvature to distribute the stress, since the highest loads are encountered when the bolt 40 is being moved up while the bottom of the trunnion slides and rocks on the bottom of groove 53. The ridge between 62 and '72 may also be rounded oif.

When such rounding occurs intermediate the ends of the diamond shape, the trunnion may be defined as lenticular.

The flat parallel sides of each of the trunnions are spaced by somewhat less than the spacing of the parallel sides of the link groove 53 or 54- so that at its middle the thickest part of the trunnion fits the groove snugly but without binding. Geometrically, the size of the diamond is that which may be circumscribed about a circle fitting in the link groove and that which is as long or truncated in length as permitted by the thickness of the locking bolt at the shank. The dihedral angle is determined by the arc of travel between link lift and bolt iii.

The resulting diamond shaped trunnion gives not only the most generous bearing surfaces for reducing the pressure but also the largest available cross section for the utmost strength of trunnion integral with the bolt.

Moreover, at the bottom of bolt travel, the relief sides such as Hand '72 mate with the link grooves as secondary bearing surfaces to reduce the impact at this end of the travel and to definitely limit the lower end of the bolt and link travel in the open position of the gun with less dependence on constraint of the other elements. This assists in maintaining uniformity of the way the lever action handles and feels despite years of usage.

Although outwardly extending trunnions are described, they may extend inwardly from a slotted lower end of the bolt into outwardly opposed link grooves 53 and While the invention has been described in the most practical form dictated by the geometry of the parts to include trunnions carried by the bolt member 40, it will be understood that the trunnions may be carried by the link member 10 to project either outwardly or inwardly into the bolt member at side slots properly oriented from front to back provided the lower end of bolt member 40 were thick enough in this direction to accommodate the sliding of the pivot connection at these slots in the bolt member.

What is claimed is:

1. In a firearm having a receiver and a barrel mounted on said receiver, the combination comprising a sliding breech block mounted on said receiver for movement forwardly and rearwardly, a link pivoted at one end on said receiver, a finger lever pivotally and slidably connected intermediate its upper end and lower end to said link adjacent the opposite end of said link, said breech block being pivotally connected to said upper end of said lever, said lever being thus connected to said block as well as said link to impart said breech block movement, and a locking bolt slidably mounted in said receiver for movement upwardly and downwardly, said bolt having a lower end forming a slidable pivot connection with said opposite end of the link for moving said bolt upwardly against one end of said breech block and downwardly away from said breech block end through an angle of relative movement between said bolt and the link operating said bolt, said lower end slidable pivot connection comprising a trunnion on one of said bolt and said link, said connection also comprising spaced parallel upper and lower sides of a corresponding groove on the other of said bolt and said link for receiving said trunnion, said trunnion having substantially spaced parallel flat upper and lower bearing surfaces presentable at least when said bolt is moved upwardly adjacent said breech block end in substantial parallelism against either of said groove sides.

2. In a firearm having a receiver and a barrel mounted on the front of said receiver, the combination comprising a sliding breech block mounted in said receiver for movement forwardly to a breech closed position and rearwardly to a breech open position, a link pivoted at its front end of said receiver and having at its rear end a groove with spaced parallel upper and lower sides, a finger lever pivotally and slidably connected intermediate its upper end and lower end to the link adjacent its rear end, said breech block being pivotally connected to said upper end of the finger lever, said lever being thus connected to said block as well as said link to impart said movement to the breech block, a locking bolt slidably mounted in said receiver and movable upwardly to an upper position and downwardly to a lower position, said bolt having a lower end forming a slidable pivot connection with said rear end of the link for imparting movement upwardly and downwardly to said bolt, said bolt having an upper end including a wedge for bolstering the breech block at said closed position when said bolt is moved upwardly to the upper position by action of said link on said bolt lower end at said slidable pivot connection, said connection comprising opposed trunnions integral with said lower end and also opposed grooves in said link rear end each having spaced parallel upper and lower sides for receiving a corresponding trunnion, each trunnion having a pair of spaced parallel terminal bearing surfaces received in substantial parallelism with the parallel sides of a corresponding groove at said upper position and also having a second pair of spaced parallel terminal bearing surfaces received in substantial parallelism with said parallel sides of said groove at said lower position of the bolt, the surfaces of the one pair making with those of the second a fixed angle of intersection corresponding to the angle through which said locking bolt and link pivot.

3. The firearm combination of claim 2 wherein the bearing surfaces on the underside of each trunnion intersect in a ridge which is rounded off.

4. The firearm combination of claim 2 wherein the bearing surfaces define a trunnion of diamond shape.

5. In a firearm having a receiver and a barrel connected to the front of said receiver, the combination comprising a breech block slidably mounted in the topside of said receiver for reciprocation between a breech closing position and a breech open position, a link pivoted at its front end of said receiver adjacent the bottomside of said receiver, a finger lever pivota-lly connected at the upper end of said lever to said block and slidably connected at a lever slot intermediate the ends of said lever to a pivot point on said link whereby said block may be moved from one of said positions to the other by manual actuation of the other end of said finger lever, an upwardly and downwardly movable locking bolt slidably mounted in said receiver and having one end formed as a wedge adapted to be thrust into engagement against the back of said breech block to lock said block in said breech closing position, said locking bolt having a pair of opposed trunnions for sliding connection with opposed grooves at the rear end of said link whereby said link is adapted to thrust said locking bolt into wedging engagement with said block when said finger lever is pulled back and adapted to be retracted from said engagement when said lever is pulled forwardly, said trunnions having substantially parallel fiat surfaces at the lateral extremities of each trunnion for operative engagement with the opposed sides of a mating slot in said link at least when said locking bolt is first moved into and out of said wedge engagement.

6. In a lever action firearm having a breech block movable between barrel breech closing and opening positions, a locking bolt member for bolstering said breech block in said closing position by wedge action, and a lever-actuated bolt operating link member, there being a slidable pivot connection between said members for imparting a force for moving said bolt member into and out of wedge engagement with said block adjacent said closing position, the improvement in said connection comprising on one of said members a trunnion and on the other of said member opposed sides defining a mating slot, said trunnion having lateral extremities and at one of its lateral extremities a flat surface and at the opposite extremity another flat surface, said surfaces being in substantially spaced parallel relationship and operative'for engagement alternately with said slot sides at least when said locking bolt is first moved into and out of said position and engagement.

7. The firearm of claim 6 wherein the trunnion is fixed integrally to one of the members and has two pair of surfaces forming bearings at the lateral extremities of said trunnion such that one parallel pair intersect with the other parallel pair at a dihedral angle the supplement of which is substantially equal to the angle of the relative operative movement between said members.

8. The firearm of claim 6 wherein the locking bolt member has a pair of laterally outwardly directed trunnions integrally formed on said member, and wherein the slot is defined by opposed inner grooves in the link member.

9. The combination of claim 6 wherein a flat surface at one lateral extremity of said trunnion constitutes with an opposed flat surface at the opposite lateral extremity of said trunnion a first pair of bearing surfaces and wherein another flat surface at said lateral extremity constitutes with another opposed flat surface at the opposite lateral extremity a second pair of bearing surfaces.

References Cited by the Examiner UNITED STATES PATENTS 659,507 10/00 Browning 89-187 BENJAMIN A. BORCHELI, Primary Examiner. FRED C. MATTERN, JR., Examiner. 

1. IN A FIREARM HAVING A RECEIVER AND A BARREL MOUNTED ON SAID RECEIVER, THE COMBINATION COMPRISING A SLIDING BREECH BLOCK MOUNTED ON SAID RECEIVER FOR MOVEMENT FORWARDLY AND REARWARDLY, A LINK PIVOTED AT ONE END ON SAID RECEIVER, A FINGER LEVER PIVOTALLY AND SLIDABLY CONNECTED INTERMEDIATE ITS UPPER END AND LOWER END TO SAID LINK ADJACENT THE OPPOSITE END OF SAID LINK, SAID BREECH BLOCK BEING PIVOTALLY CONNECTED TO SAID UPPER END OF SAID LEVER SAID LEVER BEING THUS CONNECTED TO SAID BLOCK AS WELL AS SAID LINK TO IMPART SAID BREECH BLOCK MOVEMENT, AND A LOCKING BOLT SLIDABLY MOUNTED IN SAID RECEIVER FOR MOVEMENT UPWARDLY AND DOWNWARDLY, SAID BOLT HAVING A LOWER END FORMING A SLIDABLE PIVOT CONNECTION WITH SAID OPPOSITE END OF THE LINK FOR MOVING SAID BOLT UPWARDLY AGAINST ONE END OF SAID BREECH BLOCK AND DOWNWARDLY AWAY FROM SAID BREECH BLOCK END THROUGH AN ANGLE OF RELATIVE MOVEMENT BETWEEN SAID BOLT AND THE LINK OPERATING SAID BOLT, SAID LOWER END SLIDABLE PIVOT CONNECTION COMPRISING A TRUNNION ON ONE OF SAID BOLT AND SAID LINK, SAID CONNECTION ALSO COMPRISING SPACED PARALLEL UPPER AND LOWER SIDES OF A CORRESPONDING GROOVE ON THE OTHER OF SAID BOLT AND SAID LINK FOR RECEIVING SAID TRUNNION, SAID TRUNNION HAVING SUBSTANTIALLY SPACED PARALLEL FLAT UPPER AND LOWER BEARING SURFACES PRESENTABLE AT LEAST WHEN SAID BOLT IS MOVED UPWARDLY ADJACENT SAID BREECH BLOCK END IN SUBSTANTIAL PARALLELISM AGAINST EITHER OF SAID GROOVE SIDES. 